FR2747912A1 - INTRACORPOREAL STENT TO BE PLACED IN A BODY CHANNEL - Google Patents

Abstract

Intracorporeal endoprosthesis, characterized in that it consists of a succession of cylindrical sheaths forming long segments (6) and alternating short segments (7) linked together.

Description

The present invention relates to a stent intended to be put

  in place in a canal of the human body, especially in a stenosed artery or undergoing an aneurysm. The prior art has already made known implants or stents made of metal wire and in particular stents produced by a continuous metal wire formed in a zigzag then wound in a helix, this prosthesis being compressible and self-expanding to

  following prior compression.

  Such a prosthesis is described in FR-A-94 024475 which further proposes making the metal wire in shape memory alloy to allow stress to be exerted

  regular using the prosthesis.

  A similar prosthesis is also described in EP-A-

  0 556 850 in which wires of any cross-section are joined together to delimit a cylindrical thread surrounded by a

  wire, itself wound around a helix.

  A helically wound wire coated with a sheath to maintain the helically wound wire at a given diameter is, for

  elsewhere, described in FR-A-91 00820 to constitute an endo-

vascular prosthesis.

  This technique is also proposed by EP-A-0 380 668 which

  also describes a catheter for the placement of the endo-

  prosthesis. In addition, a wire first bent in a zigzag and then wound to form parallel helical turns is described.

  for the realization of a stent in EP-A-0 357 003.

  The above elements illustrating the prior art do not so far make it possible to apply to the internal wall of a body canal, more particularly of an artery, variable forces depending on the pathological state of this channel while ensuring that the stent is always properly held in place without risk

  damage to the channel in which it is found.

  This result is obtained by the intracorporeal endoprosthesis of

the invention.

  In accordance with the invention, the intracorporeal endoprosthesis

  consists of a succession of cylindrical sleeves forming long segments and alternating short segments15 connected to each other.

  According to another important characteristic of the invention, a shape memory alloy is used for the production of strands constituting successive turns of each cylindrical sheath, the successive turns having substantially parallel strands, when the sheaths are

  brought to the temperature of the human body.

  Various other features of the invention emerge

  moreover from the detailed description which follows.

  Embodiments of the subject of the invention are shown, by way of nonlimiting examples, in the accompanying drawing. Fig. 1 is an elevation, partly schematic, of

  the intracorporeal stent of the invention.

  Fig. 2 is a partial elevation, on a larger scale, illustrating a method of assembling elements of the prosthesis

fig. 1.

  Fig. 3 is a partial elevation, on a larger scale, illustrating another method of assembling elements of the

prosthesis of fig. 1.

  Fig. 4 is a section, on a larger scale, seen next

line IV-IV of fig. 2.

  Fig. 5 is a section, similar to FIG. 4, of a variant.

  Fig. 6 is a schematic elevation illustrating a character-

  additional benefit of the prosthesis.

  The endoprosthesis, object of the invention, is produced from wires or ribbons of shape memory alloy, for example of nickel / titanium metal alloy, which can be annealed to maintain a thermal memory corresponding to the shape given to it at the time of this annealing while this shape is modified when the wire or the ribbon is subjected to a variation of

  temperature, especially at cooling.

  We make sure that the alloy is shaped to remain stable at a temperature of the order of that of

human body.

  According to the invention, the wire or the ribbon is folded to delimit successive turns 1, 2 ... R each having the shape of a loop whose strands 3, 4 are substantially

  parallel and interconnected by a curved part 5.

  Separate segments 6 and 7 are said to be produced in the following, long segments for those designated by 6, and

  short segments for those designated by 7.

  The turns 1, 2 ... n of a segment, for example of a long segment 6, are connected to the turns of a short segment 7 by weaving, as illustrated in FIG. 2, or by a link 8 as illustrated in FIG. 3. The link 8 is, for example produced by a non-absorbable surgical suture thread or by a staple made of the same material as that of the threads or ribbons constituting the successive turns of each segment. The long segments 6 and the short segments 7 are shaped to produce cylindrical sleeves whose strands are substantially aligned when their curved parts 5 are

  joined together by weaving or by means of the link 8.

  Although a round section wire can be used for the manufacture of the endoprosthesis of the invention, it is preferred to use a rectangular segment ribbon as illustrated in FIG. 4 which shows two strands 3a, 4a of a ribbon of rectangular section whose short sides face each other while FIG. 5 shows a ribbon, also of rectangular section, but the strands 3b, 4b of which face each other by a

from their big sides.

  In addition to the above and as illustrated in FIG. 1 he

  It is advantageous according to the invention that two cylindrical sleeves

  bricks made by long segments 6 are separated by one or two cylindrical sleeves made from short segments 7 and that one or two cylindrical segments made by short segments extend the sleeves

  made by long segments 6.

  The use of sheaths made from short segments has the effect of stiffening the prosthesis at its ends and at its middle part, which facilitates its holding and its maintenance.

  in place in a body canal, for example in an artery.

  A very short prosthesis can, according to the invention, comprise only one long sheath and two short sheaths at its ends. On the contrary, a long prosthesis can comprise successive series of long sleeves and short sleeves. For example, a prosthesis having to measure 6 cm long advantageously comprises two long sleeves connected directly to each other and two short sleeves on the

  on the other of said two long sleeves.

  Many other combinations can be made according to the length which the prosthesis must have and also according to the effective diameter which it must maintain at

inside the body canal.

  The arrangement which the prosthesis must present according to which long sleeves and short sleeves are used makes it possible to adapt it to the pathology to be treated. In particular, it is advantageous to use short sheaths at the level of a stenosis to be treated while long sheaths are more suitable in arteries

with a weak wall.

  In some cases and additionally, the prosthesis is placed in a sleeve 9 illustrated in FIG. 6, this porous or non-porous sleeve obviously being made of biocompatible material and

  being intended for arteries presenting an aneurysm.

  When a sleeve 9 is provided, the ends constituted by short sheaths make it possible to ensure proper maintenance of the prosthesis on either side of the weak zone of the artery. Part or all of one or two short cylindrical sleeves can protrude from the sleeve 9 to develop a large radial force by allowing

  thus ensuring that the prosthesis is held in place.

  For the production of the sleeve 9, it is possible to use a material other than a metal, for example it is possible

  to use a polymer (silicone, gelatin, etc.).

  The invention is not limited to the exemplary embodiments, shown and described in detail, because various modifications

  can be made without departing from its scope.

Claims (8)

  1 - Intracorporeal endoprosthesis, characterized in that it consists of a succession of cylindrical sheaths forming long segments (6) and short segments alternating (7) interconnected.   2 - Endoprosthesis according to claim 1, characterized in that the long segments (6) and the short segments (7) are constituted by successive turns (1 .. 2 ... R) each formed by two strands (3, 4 ) connected by a curved part (5). 3 - Endoprosthesis according to claim 2, characterized in   that the strands (3. 4) of each turn are parallel.   4 - Endoprosthesis according to one of claims 2 or 3,   characterized in that successive turns are produced from threads or ribbons.   - Endoprosthesis according to one of Claims 2 to 4,   characterized in that the successive strands (3, 4) are of rectangular section, the short side of their rectangle is facing.   6 - Endoprosthesis according to one of claims 2 to 4,   characterized in that the successive strands (3. 4) are of rectangular section, the long side of their rectangle is facing.   7 - Endoprosthesis according to one of Claims 2 to 4,   characterized in that a shape memory alaiae is used for the production of the strands constituting the successive turns of each cylindrical sheath, the successive turns having parallel strands (3, 4),   when brought to human body temperature.   8 - Endoprosthesis according to one of claims 1 to 7,   characterized in that short cylindrical sleeves are   placed at both ends of the prosthesis.   9 - Endoprosthesis according to one of claims 1 to 8,   characterized in that sets of two short sleeves are   placed at the ends of the prosthesis.   - Endoprosthesis according to one of Claims 1 to 9,   characterized in that the assembled sleeves are arranged in a sleeve (9).   11 - Endoprosthesis according to claim 10, characterized   in that short sleeves protrude from the sleeve (9).